Nanotechnology for spilled oil encapsulation, remediation and recovery

ABSTRACT

Diacylglycerol PEGs (DAG-PEGs) are used remediate oil contaminations. DA-PEGs encapsulate the oil into lipsomes in an aqueous environment. The lipsomes sequester the oil from causing damage.

RELATED APPLICATIONS

This application is a divisional application of allowed U.S. patentapplication Ser. No. 11/825,940 entitled “Nanotechnology for spilled oilencapsulation, remediation and recovery” (later changed to “Method forencapsulation, remediation and recovery of spilled oil”) filed Jul. 10,2007, Now U.S. Pat. No. 7,794,595 issued on Sep. 14, 2010, which in turnclaims priority based on U.S. Provisional Patent Application Ser. No.60/840,789 entitled “Nanotechnology for spilled oil encapsulation,remediation and recovery” filed Aug. 28, 2006.

FIELD OF THE INVENTION

This invention relates to cleaning oil contaminations and to extractinghydrocarbons from oil sands.

BACKGROUND OF INVENTION

Part A: Oil Contamination

The environmental and health effects of the average 3,000 oil spillsannually worldwide have untoward consequences. An environmentallyfriendly solution to clean up these spills could have tremendous valueto both the geographic region and the biological habitat where the spilloccurs. A non-toxic, nano-scale solution to cleaning up petroleum spillsboth on land and in water is described.

Part B: Extraction of Hydrocarbons from Oil Sands

Oils sands contain a large amount of the world's potential oil reserves.Oil-sand, also called tar sand, is an earthy, dark gray substance with ashiny finish found in various size clumps or clods with a characteristictar and oil odor. At the same time, it is both greasy and grainy to thetouch. It is comprised of sand, clay, bitumen and a small amount ofwater. Tar sands are mined to extract the hydrocarbon-rich bitumen,which is then converted into synthetic crude oil or refined directlyinto petroleum products, like gasoline, heating oil, fuel oil andheating oil. Bitumen is a viscous semisolid that can be refined intosynthetic crude oil. However, in the Northern Canadian oil sand fieldsit is trapped in the sand and clay and does not flow at ambient groundtemperatures, all of which makes it difficult and expensive to extract.Even in warmer climates, bitumen is difficult to extract from oil sands.

Methods of extracting the bitumen currently use hot water combined withskimming techniques and organic solvents. The process is about 85%efficient when used in surface mining and 60-65% efficient with in-situ,or underground, mining. The current methods result in high fuelconsumption and high carbon dioxide emissions. The need for aneconomical, energy efficient way to extract bitumen from sand withoutcreating excess green house gasses is critical.

BRIEF DESCRIPTION OF THE INVENTION

Oil contaminations are remediated by applying PEG lipids. The PEG lipidsencapsulate the oil into liposomes.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 shows a chemical structure of PEG-12 Glycerol Dioleate

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

PEG lipid conjugates have been found to possess useful properties fordealing with oil products. Several compositions and methods aredescribed herein.

Part A: Cleaning Oil Contaminations

When certain diacylglycerol-polyethyleneglycol (DAG-PEG) lipids areadded to the surface of an oil spill in water, the lipids will entrapboth water and oil from the immediate surroundings and disperse thecontents and vesicles into a suspension. The DAG-PEG will immediatelyand spontaneously begin to entrap water and available oil from the spillinto thermodynamically stable vesicles. Mechanical mixing via pumping orinjecting can help speed the reaction of vesicle formation andencapsulation.

If an oil contamination is on a dry or hydrophobic surface, water mustbe added to begin the process of vesiculation and oil entrapment. Aratio of about 30:4:1 (water:DAG-PEG:oil) is sufficient for oilencapsulation. If the oil contamination is on an animal, such as a birdor mammal, again water must be added to begin the process ofvesiculation and oil entrapment.

Once the oil has been entrapped into vesicles it will remain inside thebi-layers of the vesicle and in suspension indefinitely, allowing foreasy clean-up either by washing with more water or with vacuumequipment. The resulting liposome suspension is water washable and canbe cleaned off animals, including bird feathers, fur and scales.Additionally, the suspension can be broken and components separatedusing various techniques. Because these formed vesicles arethermodynamically stable, they will remain as vesicles until disruptedby high energy mechanical shear, by enzyme activity or by heat.

In the field, the DAG-PEG may be re-used. After treatment of an oilcontamination with lipid, a lipid/oil suspension forms. If thissuspension is collected, the lipid may be separated from the suspensionand reapplied to the contamination. This may be accomplished byoptionally heating the suspension and then mechanically separating lipidfrom the other components by centrifugation or other means.

The invention is useful for cleaning oil contaminations, including butnot limited to oil spills in water, oil spills on land, oilcontaminations on machinery, and oil contaminations on animals. Theinvention is useful on crude oil, refined oil, and used oil.

DAG-PEGs are non-toxic and have an LD₅₀ of >5 grams/kg, making themsuitable for cleaning environmentally sensitive areas and livinganimals. See e.g., AAPS PharmSci 2004; 6 (2) Article 14.

FIG. 1 shows the chemical structure of PEG-12 Glycerol Dioleate (“PEG-12GDO”), which includes a glycerol backbone 46, a PEG chain 48, and a tailgroup 50 having two hydrocarbon chains. Together, the backbone 46 andthe PEG chain 48 comprise the head group of the molecule.

PEG-12 GDO and similar lipids are described in co-owned U.S. Pat. No.6,610,322 entitled “Self-forming, thermodynamically stable liposomes andtheir applications”, which is hereby incorporated by reference.

PEG-12 GDO and PEG-12 GDM (glycerol dimyristate) are among preferredlipids for practicing this invention for two main reasons. First, theyare both fluid at 25 degrees C. This allows for easy application to andmixing with an oil contamination. The low melting temperature alsoallows for easy recovery and recycling of the lipid from oil/DAG-PEGsuspensions. Second, these preferred lipids both have packing parametersthat allow them to spontaneously form thermodynamically stable liposomesin aqueous solutions, thereby entrapping the oil.

Those skilled in the art will appreciate that DAG-PEGs may be made tohave varying lengths of PEG and varying lipid chains. Also, both the PEGand lipid chains may be joined to the backbone using different chemicallinkages than shown in FIG. 1. However, any DAG-PEG that is fluid at 25degrees C. and having proper packing parameters is meant to fall underthe scope of this invention.

Without being bound to a theory, it is currently believed that theoil/DAG-PEG suspensions are true liposomes with an enclosed aqueousspace and with the oil entrapped in the bilayer.

DAG-PEGs may be useful in treating oil contamination even when thewater:lipid:oil ratio is less than 30:4:1. Lipid added to oil withoutwater results in the formation of a gel. In some cases, the formation ofsuch gels might be preferable to leaving a contamination untreated ortreatment with other methods.

The invention works with many kinds of oil, including crude oil and itsvarious fractions and lubricant oils having paraffin.

In one aspect the invention is a liposome comprising oil and adiacylglycerol-PEG lipid having a melting temperature below about 25degrees C. The diacylglycerol-PEG lipid preferably has a meltingtemperature below about 15 degrees C. The weight ratio ofdiacylglycerol-PEG:oil is preferably greater than about 1:1, andpreferably greater than about 4:1. The diacylglycerol-PEG lipidpreferably is selected from the group consisting PEG-12 GDO and PEG-12GDM.

In another aspect the invention is a method of treating an oilcontamination comprising applying a DAG-PEG lipid to the contamination.The method may further comprise applying water to the lipid and oil. Thelipid preferably has a melting temperature below about 25 degrees C. Theweight ratio of diacylglycerol-PEG:oil is preferably greater than about1:1, and more preferably greater than about 4:1. The diacylglycerol-PEGlipid is preferably selected from the group consisting PEG-12 GDO andPEG-12 GDM. The method may further comprise mechanically mixing theDAG-PEG lipid with the contamination to form a lipid/oil suspension,collecting the resulting lipid/oil suspension, and separating theDAG-PEG lipid from the lipid/oil suspension.

In some cases, mixtures of diacyl-PEG lipids may be useful forsolubilizing and/or sequestering oil without the production ofliposomes. In other cases, a portion of the lipid/oil suspension may beliposomes and another portion may be particles and structures other thanliposomes. This may be due to the DAG-PEG:oil ratio; packing parametersof the lipid; or the composition of the oil. In these cases theinvention is a composition comprising oil, water, and adiacylglycerol-PEG lipid having a melting temperature below about 25degrees C. The diacylglycerol-PEG lipid preferably has a meltingtemperature below about 15 degrees C. The weight ratio ofdiacylglycerol-PEG:oil is preferably greater than about 1:1, and morepreferably greater than about 4:1. The diacylglycerol-PEG lipid may beselected from the group consisting PEG-12 GDO and PEG-12 GDM.

Some monoacyl PEG lipids are also useful for cleaning oilcontaminations. The resulting lipid/oil suspension may include liposomesand/or other particles and structures. Mixtures of acyl-PEG lipids maybe useful for solubilizing and/or sequestering oil without theproduction of liposomes. In these cases the invention is a compositioncomprising oil, water, and a monoacyl-PEG lipid having a meltingtemperature below about 25 degrees C. The monoacyl-PEG lipid preferablyhas a melting temperature below about 15 degrees C. The weight ratio ofmonoacyl-PEG:oil is preferably greater than about 1:1, and morepreferably greater than about 4:1. The monoacyl-PEG lipid may beselected from the group consisting of PEG-8 oleate and PEG-23 oleate.

In another aspect the invention is a method of treating an oilcontamination comprising applying a monoacyl-PEG lipid to thecontamination. The method further comprises applying water to the lipidand oil. The lipid preferably has a melting temperature below about 25degrees C., and more preferably below about 15 degrees C. The weightratio of monoacyl-PEG:oil is preferably greater than about 1:1, and morepreferably greater than about 4:1. The monoacyl-PEG lipid may beselected from the group consisting of PEG-8 oleate and PEG-23 oleate.The method may further comprise mechanically mixing the acyl-PEG lipidwith the contamination to form a lipid/oil suspension. The method mayfurther comprise collecting the resulting lipid/oil suspension andseparating the acyl-PEG lipid from the lipid/oil suspension.

Even though a PEG lipid does not form a liposome in conjunction withoil, the methods described above may still be useful for solubilizing orsequestering oil.

Part B: Extraction of Hydrocarbons from Oil Sands

PEG lipids dissolve the bitumen out of oil sand resulting in a flowablemixture or solution. The flowable form is a medium body, black, shinyliquid that is eminently transportable for refining anywhere in theworld via any mechanism or method conceivable. In particular, thisflowable form may be transported via pipeline without diluent. CertainPEG lipids provide an even further advantage in that, if the mixture isspilled or leaked it is easily cleaned up because if added to water itimmediately gets encapsulated in to vesicles and can be dispersed. It'ssafer oil. Once at the refinery the PEG lipid can easily be separatedfrom the other hydrocarbons and a barrel would yield normal quantitiesof gasoline, fuel oil, lubricant oils, heating oils etc and PEG lipidfor re-use in the oil sand fields.

The inventor has found a way to extract a high percentage of bitumenfrom oil-sands using a novel method. In one aspect, the method uses adiacylglycerol-polyethyleneglycol (DAG-PEG) lipid to extract thebitumen. In the initial step 1:1 ratios (v/wt) of DAG-PEG and oil-sandare combined and mixed. It is helpful that the mixing is vigorous enoughto break down the small clumps of sand, bitumen and clay. Since noheating is necessary, very little energy is used during this phase.However, heat maybe used to expedite the process. As mixing continues,the lipid and bitumen combine and a black, shiny liquid emerges. Thislipid has the characteristics of crude oil in viscosity, appearance andodor. Once the fines and solids (mostly sand) have settled, the liquidfraction can be collected and easily transported to any destination forfurther extraction or refinement. This immediately makes bitumen lesssticky and transportable, without much energy added.

The invention may substantially reduce carbon emissions produced duringthe production of oil from coal sands. Current methods require heatinglarge amounts of water to high temperature. Such heating is expensive,both in terms of fuel costs and greenhouse gas emissions. Since the PEGlipid is a liquid at ambient temperatures and converts bitumen into aflowable form on contact, it is possible to extract hydrocarbons withoutthermal input. Our estimate is that this new method will only take 38 kgof CO2 equivalents per barrel of oil extracted compared to the current85.5 kg CO2 equivalents per barrel.

An additional advantage of the invention is that the flowable PEGlipid-bitumen combination is more easily transportable than bitumenextracted by current means.

After a single extraction, some bitumen remains with the clay and sandfractions. Additional hydrocarbons may be extracted by further PEG lipidtreatment. Such treatment may be done in steps or continuously.

As a final step, the addition of ambient temperature water to themixture of liquid will wash the sand and clay of remaining PEG lipid andmost of the bitumen. As water is added the PEG lipid forms nano-sizedvesicles. As the vesicles form they encapsulate the lipid solublebitumen in the interior of the vesicles and remove the bitumen from thepores of the sand particles. The vesicle/water/bitumen fraction ispumped to a processing station to distill off the water.

Mixing and/or heating enhance the rate of conversion of hydrocarbonsinto a flowable form. In practice, heating may be most advantageousduring in situ mining, and mixing may be most advantageous when the oilsands are excavated and the extraction process is performed aboveground. The mixing may include grinding the oil sand into particles toprovide more surface area for the oil sand to interact with theextraction polymer.

The method is useful when the oil sands have been extracted to an aboveground location. A particular advantage of above ground extraction isthat the oil sand is more easily ground into particles, preferably fineparticles.

This method can also be used for the in situ reserve extraction ofbitumen from sand. Challenges facing current in situ process areefficient recoveries, management of water used to make steam, andco-generation of all (otherwise waste) heat sources to minimize energycosts.

The in situ process consists of pumping a PEG lipids into the in situreserves both horizontally and vertically, similar to the steamextraction patterns currently used. Once the DAG-PEG has been pumpedinto the oil-sand store site below the surface a production well pumpcan easily pump the DAG-PEG-bitumen liquid and it can be transported tothe refining site. Heating the DAG-PEG to about 35 degrees C. prior topumping it in situ is helpful in obtaining higher bitumen recovery.Repeating this process 2-4 times will increase yields.

The last phase of in situ mining is to pump ambient temperature waterthrough the same system that the DAG-PEG lipid was introduced andremoved. This will cause the DAG-PEG to form vesicles and remove some ofthe remaining bitumen.

Once the water/lipid/bitumen has been removed from the ground thevesicles can be broken with heat of about 50 degrees C. and the watercan be distilled off and the resultant lipid-bitumen mixture can beshipped to a refining facility.

One advantage to the lipid-bitumen combination is that it isenvironmentally friendly. If this liquid is spilled into waternano-vesicles spontaneously and immediately form around the lipidsoluble bitumen and disperse into the water column. The nano-vesiclesare stable, non-toxic and eco-friendly. If it leaks out of a pipelineand onto the ground it can easily be cleaned up with water.

In one aspect the invention is a method of extracting hydrocarbons fromoil sand, the method comprising locating the oil sand, providing adiacyl-PEG polymer in contact with the oil sand, allowing the polymer toconvert the hydrocarbons in the oil sand into a flowable form, andcollecting the flowable form. The method may further comprise separatingthe diacyl-PEG polymer from the hydrocarbons. The diacyl-PEG polymer maycomprise a glycerol backbone. The diacyl-PEG polymer preferably has amelting temperature below about 25 degrees C., and more preferably belowabout 15 degrees C. The diacyl-PEG polymer may be selected from thegroup consisting of GDO-12, GDO-23 and GDL-23. The location of the oilsand may be underground or above ground. The method may further comprisepreheating the diacyl-PEG polymer and/or grinding the oil sand intoparticles.

The invention is also a method of converting hydrocarbons from oil sandinto a flowable form comprising locating the oil sand and providing adiacyl-PEG polymer in contact with the oil sand. The diacyl-PEG polymercomprises a glycerol backbone. The diacyl-PEG polymer preferably has amelting temperature below about 25 degrees C., and more preferably belowabout 15 degrees C. The diacyl-PEG polymer may be selected from thegroup consisting of GDO-12, GDO-23 and GDL-23. The location of the oilsand may be underground or above ground. The method may further comprisepreheating the diacyl-PEG polymer and/or grinding the oil sand intoparticles.

The invention is also a method of extracting hydrocarbons from oil sand(tar sand) comprising locating the oil sand, providing an acyl-PEGpolymer in contact with the oil sand, allowing the polymer to convertthe hydrocarbons in the oil sand into a flowable form; and collectingthe flowable form. The method may further comprise separating theacyl-PEG polymer from the hydrocarbons. The acyl-PEG polymer preferablyhas a melting temperature below about 25 degrees C., and more preferablybelow about 15 degrees C. The acyl-PEG polymer may be selected from thegroup consisting of PEG-23 oleate and PEG-8 oleate. The location of theoil sand may be underground or above ground. The method may furthercomprise preheating the diacyl-PEG polymer and/or grinding the oil sandinto particles.

During the process of extracting hydrocarbons from oil sands, usefulcompositions may be produced. Therefore, the invention also includes acomposition comprising oil sand and a diacyl or acyl-PEG polymer incontact with the oil sand. The composition further comprises a flowableform of hydrocarbons from the oil sand solubilized by the polymer.

The methods described for diacyl-PEG lipids may be similarly useful forcertain monoacyl-PEG lipids. Unsaturated lipids conjugated to relativelyshort PEG chains (8-23 subunits) are expected to be among the mostsuitable polymers in this category.

General Considerations

DAG-PEG lipids with low melting points are preferred lipids for bothsequestering oil contaminations and extracting hydrocarbons for bitumen.While the exemplary DAG-PEG in FIG. 1 has a glycerol backbone andspecific linkages between the backbone, acyl groups and PEG chain, thoseof skill in the art will realize that similar molecules will also besuitable for practicing the inventions disclosed herein. For example,different chemical linkages and different backbones may be used toconstruct DAG-PEG lipids.

Similarly, monoacyl-PEG polymers may be constructed with a variety ofchemical linkages.

Though polymers with low melting points are preferred, compounds withhigher melting points may also be used in practicing certain aspects ofthe invention. For example, GDO-45, GDM-45 and GDP-23 all have meltingtemperatures higher than 25 degrees C. However, when heated to a liquidphase these polymers are useful for both sequestering oil contaminationsand extracting hydrocarbons for bitumen.

Combinations of polymers are also useful. Since particular polymers mayvary slightly in their ability to interact with the various fractions ofoil and bitumen, it may sometimes be useful to tailor a combination ofPEG-lipid conjugates to a particular application.

In a broad sense, when water is not present the invention is a flowablemixture of PEG-lipid and hydrocarbons/oil. When water is present, theinvention is a lipsome comprising PEG-lipid and hydrocarbons/oil.

The invention may be used for hydrocarbon extraction from oil sand byomitting the step of extracting without water. In such a case, the useof water will result in liposomes and/or other structures suspended inan aqueous solution. Such a process may be useful to recover remainingfractions from oil sands previously processed by conventional methods.

When relatively small amounts of DAG-PEGs are added to oil in an aqueousenvironment liposomes form spontaneously, thereby entrapping some of theoil. Similarly, adding relatively small amounts of PEG lipids to bitumenresults in converting hydrocarbons to a flowable form. For bettercleaning/extraction, the PEG lipids should be applied in larger amountsand repeatedly, if necessary.

Both flowable hydrocarbon/PEG lipid mixtures and oil/liposomesuspensions may require extra separations before extraction, recovery orrefining processes can be done. There is typically about 12% water inoil sands. Much of this water will be taken up in the flowable form andmust later be removed, as must the water in the liposome suspensions.Also, fine components in bitumen may require gravitational separationsuch as centrifugation or inclined plate settling.

The compositions and methods described are suitable for extractinghydrocarbons from oil sand, oil shale, tar sand, or any similar deposit.

While preferred embodiments of the present invention have beendescribed, those skilled in the art will recognize that other andfurther changes and modifications can be made without departing from thespirit of the invention, and all such changes and modifications shouldbe understood to fall within the scope of the invention.

EXAMPLE 1 Entrapment and Dispersion of Oil in Water

HD 30 motor oil was added to water. Then PEG-12 GDO was added in a 1:4ratio (oil:PEG-12 GDO). An opaque white suspension formed which showedliposomes when examined under a light microscope at 600×. The oil wasentrapped and dispersed in the suspension.

EXAMPLE 2 Cleaning an Environmental Oil Spill (Predictive)

A large quantity of medium weight crude oil is spilled from a rupturedtanker and the oil washes onto a coastal area. The water temperature is45 degrees C. and the air temperature is 50 degrees. The beach issprayed with diacyl lipid-PEGs to disperse the oil, thereby formingliposomes.

EXAMPLE 3 Recovery of Hydrocarbons from Oil Sand

These experiments were conducted at room temperature, about 22° C.

The objective of this experiment was to test various non-toxic solventsfor their ability to release bitumen from Canadian oil-sand.

The goal of this experiment was to find the relative solvent capabilityof various solvents and compare them to identify the best solvents forthe purpose of releasing bitumen from oil-sand at low energy expense anddecreased green-house gas release.

Table 1 lists the solvents tested. All solvents were fluids at ambienttemperature. A weighed amount of each solvent (between 15 grams and 35grams) was put into a Pyrex mortar and pestle. An equal amount ofCanadian oil-sand was weighed and put into the solvent. The 1:1 mixturewas left to stand for 10 minutes then triturated for 2 minutes and leftto stand for 10 minutes. Solubility was graded by observation of thecolor of the liquid which correlates to the amount of bitumen that hasbeen released from the sand and into the solvent. The darker the liquid,the more bitumen was released. In the second step the resultant liquidwas decanted off and more solvent was added to the oil-sand+residualsolvent in the mortar. The mixture was allowed to stand for 10 minutesand then triturated for 2 minutes then allowed to stand for 10 moreminutes. The resultant liquid was observed for color change, odor andclarity and decanted off. The process was repeated a third time. Theresultant decanted liquid, collected during all phases was observed forsolubility capacity. Using a scoring scale for solubility from 0-10,where 0 is insoluble and 10 is totally soluble each solvent was scored.(Table 1) The scoring table categorizes the solubility scores into fourcategories: is=insoluble (0), ss=slightly soluble (1-3), ms=moderatelysoluble (4-6), s=mostly soluble (7-9) and ts=totally soluble (10).

TABLE 1 Solubility Scores of Various Solvents for Canadian Oil SandSolubility* Melting Slightly Moderately Mostly Totally Solvent Temp ° C.Insoluble Soluble Soluble Soluble Soluble Isopropyl alcohol −88.5 1Ethyl alcohol −117.3 1 Benzyl alcohol −15.19 4.5 Olive oil −6 0.5Safflower oil −16 0 Soybean oil −16 0 Borage oil −12 0.5 Castor oil −180 Sesame oil −14 0 Corn oil −15 0 Glycerin 17.8 0 Propylene glycol −59 0Butylene glycol −50 0 Ethoxydiglycol −35 1 Isopropyl myristate 3 3Acetylated lanolin alcohol 6 6 Isocetyl stearoyl state 4 7 Lenoleic acid−12 9 Linolenic acid −14 9 Oleic acid −16 9 Caprylic/Capric triglyceride5 6 Sorbitan Oleate PEG-8 12 7 PEG-4 10 1 PEG-12 Glyceryl Dioleate 10 10(GDO-12) PEG-12 Glyceryl Dimyristate 15 9 (GDM-12) PEG-23 GlycerylDimyristate 16 9 (GDM-23) PEG-23 Glyceryl Dilaurate 8 10 (DGL-23) PEG-23Glyceryl Dioleate 12 10 (GDO-23)

EXAMPLE 4 Recovery of Hydrocarbons from Oil Sand (Predictive)

Additional solvents are tested for their ability to convert bitumen intoa flowable form. The experiment is carried out as in Example 3, exceptthat it is done at a temperature of 40 degrees C. The solvents in Table2 all achieve a solubility score of 9 or 10.

TABLE 2 Various Solvents for Canadian Oil Sand Melting Solvent Temp ° C.PEG-23 Glyceryl Dipalmitate 31.2 (GDP-23) PEG-45 Glyceryl Dimyristate33.2 (GDM-45) PEG-45 Glyceryl Dioleate 36.3 (GDO-45)

EXAMPLE 5 Recovery of Hydrocarbons from Oil Sand (Predictive)

PEG-23 oleate is tested for its ability to convert bitumen into aflowable form. The experiment is carried out as in Example 3. Thesolvent achieves a solubility score of 9 or 10.

1. A liposome comprising: crude oil; and a diacylglycerol-PEG lipidhaving a melting temperature below about 25 degrees C.
 2. The liposomeof claim 1, where the diacylglycerol-PEG lipid has a melting temperaturebelow about 15 degrees C.
 3. The liposome of claim 1, where the weightratio of diacylglycerol- PEG: crude oil is greater than about 4:1. 4.The liposome of claim 1, where diacylglycerol-PEG lipid is selected fromthe group consisting of PEG-12 GDO and PEG-12 GDM.
 5. A compositioncomprising: crude oil; water; and a diacylglycerol-PEG lipid having amelting temperature below about 25 degrees C.
 6. The composition ofclaim 5, where the diacylglycerol-PEG lipid has a melting temperaturebelow about 15 degrees C.
 7. The composition of claim 5, where theweight ratio of diacylglycerol-PEG: crude oil is greater than about 4:1.8. The composition of claim 5, where diacylglycerol-PEG lipid isselected from the group consisting PEG-12 GDO and PEG-12 GDM.